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DESCRIPTION JPS5983500

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DESCRIPTION JPS5983500
[0001]
FIELD OF THE INVENTION The non-invention relates to an ultrasound probe for use in an
ultrasound diagnostic layer device or the like. [Prior Art] Conventionally, as piezoelectric
ceramics of this type, so-called PZT-based pressure main piezoelectric ceramics containing lead
zirconate titanate (pbZrOs pb'r j Os) t = main component have been used, but the frequency is 5
MH 2 'i If it exceeds, it will be difficult to form a PZT based piezoelectric ceramic array probe. In
PZT-based ceramics, not only thickness vibration necessary for ultrasonic wave generation but
also transverse vibration in the width direction is strongly excited. Therefore, in order to drive
the transducer as the ultrasonic transducer at a predetermined frequency without the influence
of unnecessary lateral vibration, the transducer shape is limited. At this time, the thickness of the
vibrator is determined by the frequency, and the width of the vibrator is determined so that the
influence of unnecessary vibration does not occur. In the case of PZT-based ceramics, assuming
that the thickness f ? and the width of the oscillator are W, practically it is used in the range of *
/ l (the range of 1 is the largest and the conversion efficiency is r / l = 0.5 It is known to be the
case of 0.8. Therefore, in order to obtain an efficient glove without the influence of the abovementioned unnecessary vibration, it is necessary to divide the vibrator corresponding to one
electrode into multiple and drive a plurality of vibrators by one electrode. With reference to FIG.
1 of the prior art, the division method of the transducer of the ultrasonic glove for 3,5 MHZ using
PZT-based ceramic will be described. The thickness t of the vibrator 1 is determined to be 0.4 ran
so that the frequency of the vibrator becomes 3.5 MHZ. Further, since the optimum width in this
case is w / l = 0.68, W- = 0.27 + o +. The glove is fixed to one electrode 2 as a pair of two
vibrators. Only in such a complicated configuration, unnecessary vibration can be obtained and
maximum efficiency can be obtained. In actual production, after the electrode 2 is provided on a
large-area vibrator and fixed to the backing material 3, only the vibrator portion is cut so that
three vibrators are provided per electrode. By the way, since a medical ultrasound diagnostic
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apparatus can display moving images in real time, is easy to operate, and is excellent in safety, it
is widely used for organ diagnosis and the like. In recent years, there has been an increasing
demand for the performance of organs alone by further improving the sensitivity and resolution
of these devices to totally improve the image quality. In order to improve the image quality, it is
conceivable to increase the resolution by increasing the frequency of ultrasonic waves. For
example, in the case of producing the entire globe for SMH2 using PZT-based ceramics, the width
of the vibrator becomes about 0.2 harmonic degree, and it becomes difficult to cut it into an
array at frequencies higher than this.
Therefore, in recent years, an ultrasonic probe using lead titanate-based ceramics has been
studied for the purpose of significantly relaxing the above-described restriction on the width of
the vibrator. This is because the unique characteristics of lead titanate-based ceramics, that is, (1)
the electromechanical coupling coefficient kt of thickness longitudinal vibration, is extremely
large compared to that of width direction vibration (kt / kp = 5 to 10 .Kt = 45 to 50%). (2) The
dielectric constant is low (63 to 3 ": = 200). Etc. because it is suitable for high frequency. In
particular, in this material, as shown in (1), since the kp is smaller by one digit or more than that
of the PZT-based ceramic, the vibration in the width direction is hardly excited. Therefore, even if
the width dimension sound of the vibrator is increased, the influence of the vibration in the width
direction is small, and the restriction of the width of the vibrator is greatly relieved, and w / l can
be used up to 0.5 to 2.0 . FIG. 2 also shows an element division configuration of a high frequency
glove using a conventional lead titanate-based ceramic, and the electrode 2 and the backing
material 3 are the same as in the case of using a PZT-based ceramic. The vibrator 4 using this
lead titanate ceramic sound can be made to correspond to the electrode 2 one by one, and it has
been confirmed that the response to the pulse waveform is not the same as that of the prior art.
However, even if this lead titanate-based ceramic is used, (1) there is a limitation in W / l, (l) l (t =
45 to 50% because of small sensitivity, etc.) Further, development of an ultrasonic probe using a
material having a large k t / k p and k t is desired. [Object of the Invention] The object of the
present invention is to provide a high-frequency ultrasonic probe having a simple structure and
high sensitivity, using lead zirconate-based porcelain as an ultrasonic transducer (vibrator). is
there. SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
provides a lead zirconate titanate piezoelectric material to which manganese and lead niobate are
added. Here, lead zirconate based ceramics used in the present invention will be described. Pure
lead zirconate ceramic (PbZr03) is an antiferroelectric (orthorhombic thread) having a curiosity
point at 230 C and is not electrostatic. If lead titanate (PbTjOs) with a small amount of lid is
added to it, or manganese / lead niobate (Pb (Mnx / aMb2 / 3) Os) as the third component, it
becomes a ferroelectric (rhombohedral system), It becomes piezoelectrically active by
polarization processing. Such a ceramic is represented by the general formula xPbZrOs +
YPbTtO3 + ZPb (Mnx / aMbv'a 103 (1), where x 10 y + Z = 1 (1) kt and lct / kp are thick.
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(2) Six crystals are small. (3) Q is high. These materials are more suitable for higher frequency
than conventional lead titanate ceramics and have characteristics. Lead zirconate based ceramics
containing such characteristics have, for example, the amount of PbZrOs in the formula (1) x = 0.
'125, amount of PbTiOs'! It is obtained by the composition of = 0.05, Pb (Mn t / sMb 2/3) 03
amount Z = 0.025. The characteristics of this ceramic are: kt = 61%, k t / k p = 20.3, '3' 3 = 165,
Q M = 31001: h. The ultrasonic probe using the piezoelectric material of the present invention is
completely the same as the structure of the conventional probe shown in FIGS. 1 and 2, and
known techniques can be applied. Therefore, the description of the structural operation principle
and the like of the ultrasonic probe is omitted. Hereinafter, an embodiment of the present
invention using such a lead zirconate-based ceramic will be described with reference to the
drawings. DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 3 shows the dependence of the
electromechanical coupling coefficient of the above-mentioned ceramic gold circle on the ratio
(W / l) of the width W of the @ transducer and the thickness t. Here, since k e depends on w / t, it
is defined as an effective electromechanical coupling coefficient of the oscillator. In the figure,
the thickness vibration A and the spurious vibration (width direction vibration) B are coupled in
the vicinity of W / l = 0.9 and 2.2, that is, both vibration modes are degenerated. However, it is
understood that the coupling coefficient of the width direction vibration B in the other w / (areas
is extremely small, and the influence of the width direction vibration is extremely small even if w
/ l becomes about 4.0. Furthermore, the coupling coefficient of thickness vibration A exceeds 6%
by 6 and experiments have confirmed that the sensitivity to the pulse waveform is also
comparable to that of the conventional PZT-based ceramics. An example of a pulse response
waveform is shown in FIG. 4, but a pulse of about 1 ?s is obtained even if W / l becomes 3.0.
[Effects of the Invention] As described in detail above, according to the present invention, highsensitivity ultrasonic waves for high frequency can be obtained by using lead zirconate-based
ceramics fully doped with manganese and lead niobate as the ultrasonic transducer (vibrator). A
probe can be provided.
[0002]
Brief description of the drawings
[0003]
1 and 2 show element division configurations in the ultrasonic probe, and FIG. 3 shows that the
effective electromechanical coupling coefficient of the S @ element using the present invention
has a transducer width W and a thickness t. FIG. 4 is a diagram showing that it depends on the
ratio w / l, and FIG. 4 is a diagram showing a pulse response waveform when W / l is changed in
FIG.
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1 иии Vibrator, 2 иии Electrode, 3 иии Backing. 1st 3rd chart width w / gravity of width n / F ? F 54 ?
4 Figure I и QP '/ d +' y
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